查看更多>>摘要：Directional solidified TiAl alloys have low density and good comprehensive high temperature performance, which is an ideal substitute material for high temperature structural parts. In this paper, phi 16.5 mm directional solidified Ti-45Al-5Nb sample with full-lamellar microstructure was prepared successfully by electromagnetic confinement technique at 10 mu m/s and relative tensile tests at 800 degrees C were also performed. The tensile strength of Ti-45Al-5Nb alloy at 800 degrees C is 765 MPa and the elongation is 16%. Moreover, results of tensile process characteristics and fracture analysis show that this material has two distinct fracture mechanisms at 800 degrees C, which are cleavage fracture mechanism and microporous aggregation fracture mechanism. Two fracture mechanisms do not exist at the same time, and for a particular specimen, the fracture process is dominated by only one of them. Different fracture mechanisms are determined by the lamellar orientation difference and element segregation. When the orientation of adjacent grains is similar and the segregation is light, the fracture process is dominated by the cleavage fracture mechanism. Otherwise, proportion and scale of the gamma phase at the grain boundary increase and the B2 phase is generated. In this case, the microporous aggregation fracture mechanism will dominate the fracture process. (c) 2022 Elsevier B.V. All rights reserved.
Littlehailes, HughHendren, William R.Bowman, Robert M.Huang, Fumin...
6页
查看更多>>摘要：The optical properties of thin films of intermetallic Au3Hf were experimentally investigated for the first time, which display significant negative epsilon' in the visible and near infrared regions, hence are clearly plasmonic materials. In contrast to similar alloys, such as films of Au3Zr, the films express more negative epsilon' values and lower epsilon '' values across most of the wavelengths (370-1570 nm) investigated. The Au3Hf films were fabricated by DC magnetron sputtering at a range of deposition temperatures, from room temperature to 415 degrees C, and annealed at different vacuum levels. The films mostly formed as a combination of Au3Hf, Au2Hf and Au4Hf phases when deposited below 400 degrees C, and exclusively Au3Hf phase at above 400 degrees C, indicating key conditions for isolating this phase. The films were stable when annealed at 10(-8) Torr, but when annealed again at 10(-6) Torr the films oxidised and changed into a mix of Au-Hf phases, suggesting resistance to oxidization may be an issue for unencapsulated applications at elevated temperatures. (C) 2022 Published by Elsevier B.V.
查看更多>>摘要：The search for simply synthetic strategies of small-size metal nanoparticles is of significant relevance but still faces challenges. In this paper, a method of lowtemperature regulation (LTR) of ultrafine palladium nanoparticles deposited on porous carbon nanosheets is proposed for efficient dehydrogenation of ammonia borane. The LTR method might relieve the sintering of metal particles, thereby resulting in ultrafine Pd nanoparticles of 1.7 nm and their high dispersion on porous carbon. As suggested by the catalytic experiments hereby, Pd/NPC-LTR contributes to higher turnover frequencies of ammonia borane hydrolysis relative to most Pd-based catalysts reported previously. Furthermore, the catalytic performance could be further enhanced by the addition of NaOH under the same reaction conditions, with the hydrolysis completion time shortened by 2.5 times. Moreover, the recycle tests reveal that Pd/NPC-LTR catalyst has good stability and reusability in the hydrolysis of ammonia borane, preserving 70% of its initial catalytic activity even after 10 recycles. The insights reported here can be easily extended to slick preparation and rational design of Pd-catalysts for practical applications. (C) 2022 Published by Elsevier B.V.
查看更多>>摘要：NiFe(2)O(4 )has attracted great attention in the field of energy storage, but its application is limited due to the serious volume expansion. NiO@NiFe2O4/CNTs triphase hybrids were tailored through simple hydrothermal method with the regulation of CNTs content in triphase hybrids. The results of electrochemical performance study indicate that NiO@NiFe2O4/90CNTs triphase hybrid with CNTs content of 61.759% exhibits high discharge specific capacity of 721.65 mAh g-1 at 0.1 A g(-1) after 100 cycles, and almost 1000 mAh g(-1) at 0.5 A g(-1) after 300 cycles. The distinguished electrochemical performance is due to the synergistic effect of NiO@ NiFe2O4 and CNTs, as well as the tailoring of NiO@NiFe2O4/CNTs triphase hybrids. This work demonstates that NiO@NiFe2O4/CNTs triphase hybrid is a superb anode material for lithium-ion batteries and the importance of tailoring materials, providing new insights for searching next generation of lithium storage materials. (C)& nbsp;2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：3 vol% TiB2 nanoparticles were added to an Mg-4Al-1.5Si alloy through semi-solid stirring followed by ultrasonic vibration to refine coarse Mg2Si phases. The effect of the added TiB2 nanoparticles on the size and morphology of the Mg2Si phases as well as the mechanical properties of the magnesium alloy was investigated. The experimental results showed that under the synergistic action of ultrasonic vibration and heterogeneous nucleation of TiB2 nanoparticles, the primary Mg2Si phases were not only refined from coarse dendritic to fine blocky shape but also uniformly dispersed. The morphology of the eutectic Mg2Si phases was transformed from coarse Chinese scripts to fine short strips. The Vickers-hardness, ultimate tensile strength, and yield strength of the obtained composites were increased by 101.8%, 69.8%, and 10.6%, respectively, compared with the matrix alloy, and the elongation was enhanced from 3.2% to 9.2% especially. The fracture mode was transformed from brittle fracture of the untreated Mg alloy to ductile fracture of the composites, indicating that the TiB2 nanoparticles play an effective role in strengthening and toughening Mg-Al-Si alloys. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Fabrication of low-cost, stable and highly efficient catalysts for clean energy and environmental control applications is an urgent task. In this work, we have successfully synthesized a multifunctional two-dimensional rare earth-based LaOCl@hcp-Ni heterostructure via a simple one-pot method. Here, the semiconductor LaOCl nanoparticles were well deposited on the metastable metal hcp-Ni, and the hexagonal close-packed structure of hcp-Ni matched the layered-structure LaOCl to form a highly active LaOCl@hcp-Ni Schottky catalyst. Furthermore, LaOCl@hcp-Ni were tested for Photoelectrochemical (PEC) oxygen evolution reaction (OER) in alkaline media and the photocatalytic (PC) degradation of Rhodamine B (RhB) in aqueous solution. LaOCl@hcp-Ni shows excellent PEC-OER catalytic activity and RhB degradation performance under artificial simulated sunlight. This enhancement of PEC and PC performance is due to the Schottky interface constructed by the coupling of hcp-Ni and LaOCl, which generates an interface electric field to effectively promote the transfer of photogenerated electrons from the semiconductor LaOCl to the metal hcp-Ni through the interface. Thus, energy band gap of LaOCl with oxygen defects is adjusted to the visible light region and their valence state of La is lowered, realizing high-efficiency visible light catalytic activity. Thus, it would be a potential rare earth-based Schottky catalyst, which can be used for the PEC oxygen evolution and the PC degradation of organic pollutants.(c) 2022 Published by Elsevier B.V.
查看更多>>摘要：Artificially designing and preparing composites with unique structure is one of important ways to effectively improve the electromagnetic wave absorption performance. In this study, binary flower-like WS2 /Co hybrid composites through anchoring WS2 nanoclusters on Co nanosheets have been successfully developed. Attributing to the hierarchical structure of the composites, the effective interfacial polarization verifying from distinct Cole-Cole semicircles could improve the dielectric loss substantially, also it enabled the multiple reflections of the incident waves which benefitted for promoting the energy dissipation. Furthermore, the host of lamellate Co could maintain the magnetic characteristic and supply the magnetic loss dominantly caused by natural and exchange resonance deriving from the high planar anisotropy, the guest of WS2 nanoclusters could induce dipole polarization deriving from vacancies of W and S atoms. As a result, excellent wave absorption performance could be achieved for the composites with the minimum RL (RLmin) of - 46.5 dB at 10.2 GHz under a small thickness of 1.7 mm, accompanied by a wide effective bandwidth (RL < -10 dB) covering from 2.7 to 18 GHz with integrated thicknesses from 1.0 to 5.0 mm. Prospectively, this work provides a new opportunity to fabricate the valuable materials for practical electromagnetic wave absorbing applications. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Low mechanical performance is the key technical problem for metal-based soft magnetic composites (SMCs) with core-shell structures needed to be urgently resolved for their actual applications due to the limitation of their conventional preparation methods. In this work, dense sintered Al2SiO5 ceramic layers have been in situ formed and entirely coated on the surfaces of high-purity deformed Fe particles via a low temperature solid-phase reaction between initially-coated amorphous nano-Al2O3 and nano-SiO2 to obtain a new ceramic-reinforced Fe/Al2SiO5 SMCs. The fully-densified Fe/Al2SiO5 SMCs exhibit a high transverse rupture strength value of 120 MPa, which exceeds those for most of present metal-based SMCs. These ceramic-coated Fe-based composites also show strong corrosion resistance in water-air and salt-water conditions due to the anti-corrosion Al2SiO5 coating layers completely isolating the deformed Fe particles from the corrosion environments. Good magnetic performance is maintained in these high-strength and corrosion-resistant Fe/Al2SiO5 SMCs due to the suitable thickness of Al2SiO5 coating layers, which promises their broad application prospects for high-power electromagnetic devices in critical environments. Moreover, the fabrication for fully-densified functional metal-ceramic composites by a nanoscale solid-state reaction coating method in this work can provide a new insight for the research and applications of the other new-type metal-based composites. (c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：In this study, hexagonal boron nitride (h-BN) -polyetherimide (PEI) composites were prepared by a simple solution casting method, where the h-BN particles were aligned by an external magnetic field. Prior to the preparation of the composite samples, the h-BN platelets were firstly decorated by iron oxide nanoparticles (Fe3O4) to achieve the desired magnetic properties. Due to the alignment of h-BN particles, the composite exhibited greatly enhanced thermal conductivity along that direction. At a filler loading of 20 wt%, an enhancement of 166% was obtained, compared to that of the unaligned composite. Furthermore, the composite samples showed a low dielectric loss (~ 0.01) with the filling ratio below 20 wt% and a tensile modulus of up to 2.34 GPa. Bearing such thermal conductivity, electrical insulation properties, and mechanical properties, these composites with magnetically aligned h-BN particles show potentials for microelectronic packaging applications.(C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：A porous FeCoNiCr high entropy alloy (HEA) coating was prepared on steel substrate via vacuum sintering. Wetting behavior of liquid Al-12Si alloy over coated and uncoated steel substrate was comparatively ana-lyzed. The results show that the liquid Al-12Si alloy droplets were quickly spread and infiltrated into the porous structures under the enhanced capillary force by the micro-channels in the porous coating. A complete wetting similar to 0 degrees contact angle (CA) was thus achieved; however, the CA was up to 41.2 degrees in the case of uncoated steel substrate. In the case of uncoated steel substrate, the interfacial microstructure consisted of theta-Al13Fe4, eta-Al5Fe2 and tau(1)-Al2Fe3Si3, while it changed to Cr-enriched FCC, AlFe-enriched BCC and AlNi-enriched B2 +Al-enriched BCC eutectic-like structure embedding in the HEA skeleton. The suppression of the formation of intermetallic compounds (IMCs) at the interface was mainly attributed to the sluggish diffusion and HEA effects of the porous coating. The altered interfacial metallurgical reactions and the enhanced capillary force were contributed to the improvement of wettability. This research provides a new method for improving the wettability and suppressing the interfacial IMCs in reactive metallic wetting systems. (c) 2022 Published by Elsevier B.V.
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